1. Field of the Invention
The present invention relates to a highly reliable electrooptical device and a process for manufacturing the same, and more particularly to an electrooptical device wherein the reliability of the lead terminals have been improved.
2. Description of the Prior Art
Various electrooptical devices such as liquid crystal display devices, electrochromic display devices and electrophoretic display devices, and they are used alone or in a combination of a plurality of units, as a display device or as an optical shutter.
These electrooptical devices comprise a pair of electrode plates facing each other with a space and sealed along their periphery by a sealing material to form a cell and an electrooptical material sealed in the cell. When subjected to a reliability test such as a high temperature test or a high temperature and high humidity test, the sealed assembly is not substantially affected, but lead terminals of exposed transparent electrodes are likely to be adversely affected especially when operated under a high temperature and high humidity condition. The lead terminals are susceptible to corrosion and likely to lead to defective connection to an external circuit. In the case of watches or electric culculators, it is rare that they are subjected to such a high temperature and high humidity condition. However, in the case of instrument panels or meters for automobiles and measuring devices, it is likely that they are subjected to such a severe condition, and they are desired to have adequate durability.
In order to prevent such adverse effects, it has been proposed to form a protective layer of an electrically conductive material on the lead terminals. When such a protective layer is applied subsequent to sealing, it is difficult to form the protective layer on the lead terminals especially in the vicinity of the boudaries with the sealing material. It is likely that an unprotected portion is left along such a boundary, and such a portion is very much susceptible to corrosion since water drops, etc. are likely to deposit on the portion. In the case of a protective layer formed by vapour deposition of a metal, if tiny pin holes or unprotected portions are left, such portions are very much susceptible to corrosion, and thus, no adequate protection has been obtained by such vapour deposition of a metal.